Zonationによる空間的優先付け
シンク・ネイチャーの生物多様性重要度指標
概要
300,000種以上の生物種の分布データを用いて、全球の陸域と海域の生物多様性の重要度をランク付けした指標が、 シンク・ネイチャーの生物多様性指標です。指標の計算には、Zonationというアルゴリズムが用いられています。
分析のフロー
分析プロセスの概要を、以下の図に示しました（Figure 1）。
Figure 1: 種の分布予測に基づく空間的優先付け
ここで、Zonationによる優先付けの考え方を再度記しておきます（Figure 2）。 Zonationは、空間的な特徴量の分布データ（種の分布域など）に基づき、 保全上の優先度が低い地点を取り除いていくという逐次的な処理の繰り返しを行います。 その結果、最後に残った地点が最も重要度が高い地点ということになります。 この繰り返しの仮定で、対象とするエリア内のすべてのグリッドに対して、優先順位が計算されます。
逐次的な処理が行われることにより、ランク上位には すべての種をバランスよくカバーすることができる地点が選ばれます。
Figure 2: Zonationによる最適化のフロー
Zonationの設定
Zonationによる分析設定は次の通りです。
| Zonationの設定 | |
|---|---|
| バージョン | Zonation 5 (Moilanen et al. 2022) |
| 損失関数 | Additive benefit function (ABF) |
| 重み | 各分類群の影響が同じになるように設定。つまり、分類群 i の種数が N_i の場合、種の重み W_i は W_i = 1 / Ni となる。 |
以下に、より詳細な概要を英語で記載します。
技術的概要（英語）
Overview
Zonation is a meta-algorithm for identifying conservation priority areas (Moilanen 2007; Lehtomäki and Moilanen 2013), which prioritises each unit for biodiversity conservation by successively excluding the management unit with the least loss of the feature set (i.e., biodiversity). Moilanen et al. (2014) describes the features of Zonation as follows: "Zonation produces a complementarity-based and balanced ranking of conservation priority over the entire landscape (Moilanen et al. 2005), rather than satisfying specific targets at minimum cost". Zonation evaluates the importance of biodiversity based on how irreplaceable the biodiversity of one location is in the entire landscape. We globally computed the importance of biodiversity by using species distribution maps on a global scale as input to Zonation.
Loss function
There are two types for the model of conservation value, namely, core are zonation (CAZ) and additive benefit function (ABF). In general, the former focused on conserving the most important feature while the latter formulates an accumulation of avoided loss of features by protecting a given site. The CAZ is based on the meta-population perspective, which assumes that the distribution range (broad population size) of a species should be kept as large as possible, In our biodiversity importance metrics, we used the ABF that is based on the species-area relationship, which assumes that the extinction rate of a species should be kept as low as possible and that protected areas should be allocated in a way that maximises conservation benefits. Therefore, The ABF is generally a good choice if the features are acting as surrogates for a larger regional species pool and trade-offs between features are allowed to achieve cost-efficient coverage of species (Moilanen et al. 2014). In other words, this benefit function identifies important areas from the perspective of covering the total biodiversity, avoiding an excessive bias toward the objective of rare species conservation. Thus, in our analysis, ABF was used for the loss function.
Weighting
We used the predicted suitability layer for each species in the subsequent spatial prioritisation analyses. Terrestrial and marine realms were analysed separately. In order to remove bias of taxon-specific richness (e.g., plants have a huge number of species, while mammals have a relatively very small number of species), species were weighted as the following function: w_i = 1 / N_i, where w_i specifies the weight for species belonging to taxonomic group i and N_i represents total number of species belonging to taxonomic group i. In this weighting strategy, the weights for each species are adjusted so that each of the taxonomic groups has the same impact on the overall prioritisation, as is done in Lehtomäki et al. (2019). When using Zonation in the context of conservation practices, it is useful to include layers such as habitat conditions. In biodiversity importance metrics, however, we only used species layers in prioritisation analysis since the aim of the metrics is to show the degree of each site's importance in terms of biodiversity distribution.
Reference
- Moilanen, A., Lehtinen, P., Kohonen, I., Jalkanen, J., Virtanen, E. A., & Kujala, H. (2022) Zonation 5 v1.0rc2 (release candidate 2) software upload. Zenodo. https://doi.org/10.5281/zenodo.5899003
- Moilanen, A. (2007) Landscape Zonation, benefit functions and target- based planning: Unifying reserve selection strategies. Biological Conservation 134: 571–579.
- Lehtomäki, J., & Moilanen, A. (2013) Methods and workflow for spa- tial conservation prioritization using zonation. Environmental Modelling & Software 47: 128–137. https://doi.org/10.1016/j.envso ft.2013.05.001
- Moilanen, A et al. (2014) Zonation—Spatial conservation planning methods and software. Version 4. User Manual 290.
- Moilanen, A., Franco, A. M. A., Early, R. I., Fox, R., Wintle, B., & Thomas, C. D. (2005) Prioritizing multiple-use landscapes for conservation: Methods for large multi-species planning problems. Proceedings of the Royal Society B: Biological Sciences 272: 1885–1891. https://doi. org/10.1098/rspb.2005.3164
- Lehtomäki, J., Kusumoto, B., Shiono, T., Tanaka, T., Kubota, Y., & Moilanen, A. (2019) Spatial conservation prioritization for the East Asian islands: A balanced representation of multitaxon biogeography in a protected area network. Diversity and Distributions 25(3): 414-429.
| このページの著者 | |
|---|---|
| 五十里 翔吾 株式会社シンク・ネイチャー サービス事業部 サービス開発マネージャー |
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| 投稿日 | 2024/11/28 |
| 最終更新 | 2024/11/28 |